Include what does it do

Included files can have other extensions for example,. In SSI, the process of including takes two separate files and creates one whole file. The server takes the SSI page and inserts it into the page calling it. If the SSI calls a file that is located in another directory in the account, use include virtual instead of include file. For example:. In the above example, the header. Not really, no.

The compiler saves the original file descriptor on a stack and opens the include d file; when it reaches the end of that file, it closes it and pops back to the original file descriptor. That way, it can nest include d files almost arbitrarily. The include statement "grabs the attention" of the pre-processor the process that occurs before your program is actually compiled and "tells" the pre-processor to include whatever follows the include statement.

While the pre-processor can be told to do quite a bit, in this instance it's being asked to recognize a header file which is denoted with a. Now, a header is a file containing C declarations and definitions of functions not explicitly defined in your code. What does this mean? Otherwise, every time you wanted to use a print function like in your case , you'd have to recreate the print function.

If its not explicitly defined in your code and you don't include the header file with the function you're using, your compiler will complain saying something like: "Hey!

I don't see where this function is defined, so I don't know what to with this undefined function in your code! It's part of the preprocessor. And yes, it's just copy and paste. Usually include and include "path-name" just differs in the order of the search of the pre processor.

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This will be important if the file will only occasionally exist - e. As a rule of thumb, never include files using relative paths. If you're running scripts from below your main web directory, put a prepend. I just thought I'd mention that. It will definitely save some trouble for those users who work under Windows and transport their applications to an Unix-based server. This can be changed to wherever you store this file. Ideally includes should be kept outside of the web root. That's not often possible though especially when distributing packaged applications where you don't know the server environment your application will be running in.

In those cases I use the following as the first line. Be very careful with including files based on user inputed data. For instance, consider this code sample: index. Of course the same vulnerability exists if you are reading a file to display, as in a templating engine. You absolutely have to sanitize any input string that will be used to access the filesystem, you can't count on an absolute path or appended file extension to secure it. Better yet, know exactly what options you can accept and accept only those options.

A word of warning about lazy HTTP includes - they can break your server. If you are including a file from your own site, do not use a URL however easy or tempting that may be.

If all of your PHP processes are tied up with the pages making the request, there are no processes available to serve the include. The original requests will sit there tying up all your resources and eventually time out. Use file references wherever possible. I would like to emphasize the danger of remote includes. Now we have a file listing of Server A! I tried this on three different servers, and it allways worked.

This is only an example, but there have been hacks uploading files to servers etc. So, allways be extremely carefull with remote includes. Just about any file type can be 'included' or 'required'. By sending appropriate headers, like in the below example, the client would normally see the output in their browser as an image or other intended mime type. You can also embed text in the output, like in the example below. But an image is still an image to the client's machine. Scripts can be hidden within images or files using this method.

NEVER 'include' anything that you found on the web or that users upload or can alter in any way. To Windows coders, if you are upgrading from 5.